448 Dr. Henri Blanc on Ceratium liirundinella. 



cornutum investigated by him, the circlet of cilia described by 

 his predecessors. 



The Ceratium here treated of dies very rapidly ; out of 

 hundreds captured in the morning I have very often had 

 difficulty in tinding a few specimens in the evening ; most of 

 them were motionless at the bottom of the vessel; when 

 examined under the microscope all had the contractile part of 

 the body issuing through the ventral aperture. 



Repeoduction. 



As yet we are in possession of very few positive facts with 

 regard to the mode of reproduction of the cuirassed Cilio- 

 flagellata, and especially of Ceratium. Even among these 

 few facts there are some which have been very diiferently 

 interpreted, sometimes as demonstrating a reproduction by 

 division, sometimes as being stages of conjugation. Thus 

 Perty * thought he had observed a reproduction by longitu- 

 dinal scissiparity in a species of Ceratium, which must be the 

 same as ours ; Stein f, on the contrary, that he saw a Cera- 

 tium of the Baltic reproduce by conjugation. Pouchet| cites 

 a curious observation made by him upon individuals belong- 

 ing to the species Ceratium triiws Sind. furca ; he found these 

 attached to each other, forming chains of three, four, and even 

 eight individuals — chains which, according to Pouchet, could 

 not originate from a conjugation. Bergh§ states that he 

 has several times observed two individuals belonging to the 

 species Ceratium cornutum united to each other and having no 

 longer more than a part of their skeleton ; he is inclined to 

 believe in conjugation rather than in division. 



That such a contradiction exists in the explanation of the 

 observed facts is because none of the authors cited has paid 

 serious attention to the intimate transformations which may 

 have taken place in the protoplasm and the nucleus. Thanks 

 to the employment of histological reagents and to numerous 

 observations made upon living specimens, I can assert that 

 in all cases Ceratium hirundinella propagates hy division^ 

 after a previous division of its nucleus, 



I have stated above in describing the nucleus that it was 

 of an elongate oval form, and possessed only a single 

 nucleolus ; but this is not always the case. Fig. 6 represents 



* Perty, 'Zur Kenntniss kleinster Lebensformen,' &c. (Berne, 1852). 



t Stein, ' Der Organismns der Infusionstliiere, III. Der Organismua 

 der Flagellaten oder Geisselinfusorien,' i. Halt'te (Leipzig, 1878). 



\ Pouchet, ^' Sur revolution des Peridiniens " &c. iu ' Comptes Een- 

 dus,' tome xcv. p. 794 (1882). See also ' Annals,' ser. 5, vol. x. p. 477. 



§ Bergh, Uc. cit. pp. 214 and 268. 



